Imaging members for printers and the like are typically coated by immersing a hollow cylinder into a stainless steel dip tank that contains a liquid coating solution. The cylinder is slowly withdrawn from the dip tank, to allow the appropriate amount of solution to remain on the surface of the cylinder. This will cause the desired coating thickness to be retained after drying. Present dipping and coating methods involve gripping the cylinder at one end by a mechanical handling device.
Substrates for these imaging members are coated with at least one active electrophotographic layer, and can be made from rigid cylindrical drums as indicated above, or from flexible belts for which the present invention will be used. By manufacturing the substrate from a flexible belt rather than from a drum, the speed at which the electrostatic image is reproduced is dramatically increased. In addition, using a seamless flexible belt will eliminate problems such as seam breakage and contamination. But problems arise when attempts are made to coat flexible belts, rather than rigid cylindrical drums using known dipping and handling processes. The flexible belts from which electrophotographic imaging members are made can easily be damaged as they are handled during photoreceptor fabrication. Typical photoreceptor substrates are made from materials that include, but that are not limited to, nickel, stainless steel, aluminum, brass, polymerics, and paper. In order to prevent the belt from becoming damaged, it is best to support it along the width of its inside surface during the coating and drying process until the finished photoreceptor is cut to its final width and packaged.
In order to conserve coating material, and to provide an internal contact surface for electrical grounding or biasing it is desirable to confine the coating to the exterior surface of the belt. This is presently achieved by dipping the belt such that the axis is maintained in a vertical position. The ends of the belt must also be sealed such that air is trapped within the lower potion of the belt. This prohibits the fluid from migrating or coating the inside of the belt.
The following disclosures may be relevant to various aspects of the present invention:
U.S. Pat. No. 5,334,246 discloses a dip coat process material handling system and method for coating multiple layers of material on a hollow cylindrical member. This system is used to produce a multi-layer optical photoconductive drum, and is an example of the type of system in which the present invention may be used.
U.S. Ser. No. 08/508144 filed Jul. 25, 1995 by John S. Chambers et al pending, and commonly assigned discloses a method and apparatus for handling and dipping seamless flexible belts using a blow molded chucking device. A polymer insert is placed inside the circumference of a flexible belt, and blow molded to form a belt-carrying chucking device. The chucking device is then used to transport the belt during a dipping and coating process.
Techniques for handling and dipping these substrates as they proceed through the manufacturing process are well known. For example, U.S. Pat. No. 5,358,296 discloses an apparatus and method for holding a rigid hollow cylindrical substrate along its inside surface. The device consists of a porous substance mounted upon a fluid passageway. The porous substance is inflated until it engages the inner surface of the substrate in the radial direction. The device continues to engage the inner surface of the substrate until a suction force is applied.
U.S. Pat. No. 5,328,181 discloses an apparatus and method for transporting and coating rigid hollow cylinders. The invention consists of a mandrel which has an expandable disk at one end and a means for expanding the expandable disk at the other. The disk is expanded in a radial direction from the mandrel such that it comes into contact with the inner surface of the hollow cylindrical substrate. This results in the formation of an air tight seal between the disk and the substrate, and prevents the coating fluid from coming in contact with the inner surface of the substrate during dipping.
U.S. Pat. No. 5,328,180 discloses a rigid clamp used to grip and support tubular objects. A linkage is attached to clamping shoes which are then expanded outward in the radial direction. The clamping shoes are brought in contact with the inside surface of the tubular object.
U.S. Pat. No. 5,318,236 discloses a device which is inserted into a roll of coiled sheet material to provide support for the sheet as it is unrolled. The device consists of a hub assembly with an axle and two rotatable hub centers that are connected to support members. The support members move in the radial direction, and engage the interior surface of the hollow roll.
U.S. Pat. No. 5,314,135 discloses an expandable mandrel used to mount a core for winding a web of sheet material. The mandrel acts as a cam which slides in an outward radial direction and comes in contact with the inside surface of the hollow core.
U.S. Pat. No. 4,680,246, discloses a method for forming a photosensitive layer on the surface of a cylindrical drum by immersing the drum into a solution of photosensitive material. A fluid tight inflatable member is used to hold the drum while it is submerged in the solution. This inflatable member is tightly pressed onto the inside wall of the drum, and prevents the photosensitive solution from contacting its inside surface.
All of the references cited herein are incorporated by reference for their teachings.